1. Field of the Invention
The present invention relates to a power take-off assembly provided at a longitudinal end portion of a working vehicle for driving a working implement attached to the end portion of the vehicle. More particularly, it relates to a power take-off assembly comprising an output sleeve, which is variable in rotary speed thereof and disposed at the end portion of the vehicle longitudinally of the vehicle, and a reversible PTO shaft, whose opposite splined ends are different in their number of teeth, wherein, in correspondence to a kind of the attached working implement, one splined end of the reversible PTO shaft is selectively inserted into the output sleeve and not-relatively rotatably connected to the output sleeve so that the other splined end of the PTO shaft projects outward from the vehicle to be drivingly connected to the working implement.
2. Background Art
As disclosed in U.S. Pat. Nos. 3,513,712, 3,352,165, 3,464,277 and 5,667,330, there are well-known conventional working vehicles, e.g., conventional tractors, each of which is provided with a single PTO shaft that is splined on opposite end peripheries thereof. One end of the PTO shaft is splined coarsely (e.g., so as to form six teeth), and the other end finely (e.g., so as to form twenty one teeth). One splined end of the PTO shaft is selectively inserted into an output sleeve disposed in either front or rear end portion of the vehicle so that the other end of the PTO shaft projects forwardly or rearwardly outward from the end portion of the vehicle so as to be connected to an input shaft of a working implement attached to the end portion of the vehicle through universal joints etc. For driving a working implement requiring a low driving speed (e.g., 840 rpm), the finely splined end of the PTO shaft is inserted into the output sleeve so as to make the coarsely splined end thereof project outward. If a working implement requiring a high driving speed (e.g., 1000 rpm) is going to be driven, the PTO shaft is disposed so as to make the finely splined end thereof project outward.
The output sleeve disclosed in U.S. Pat. No. 3,513,712 is variable in its rotary speed, however, the rotary speed thereof is not changed to correspond to which of the splined ends of the PTO shaft is inserted thereinto.
Each of the output sleeves disclosed in U.S. Pat. Nos. 3,352,165, 3,464,277 and 5,667,330 is allowed to be selectively connected to one of two gear trains which are different from each other in their gear ratios. Two gears of the respective gear trains are freely rotatably disposed around the output sleeve, and an actuator for engaging one of the gears with the PTO shaft through the output sleeve is disposed between the gears. The actuator automatically engages the PTO shaft with one of the gears according to which splined end of the PTO shaft is inserted into the output sleeve.
However, such an actuator interposed in the PTO driving system tends to increase the size of the PTO speed changing arrangement which changes the rotary speed of the output sleeve. Furthermore, the actuator is not suited to a working vehicle having a lever-operated speed changing mechanism for the output sleeve.